1. Field of the Invention
The present invention relates to an automatic transmission which is mounted on a vehicle, in particular a front-engine-front-drive type car, in detail relates to a counter gear supporting device which is situated in a middle portion of an automatic transmission.
2. Description of the Related Art
The applicant of the present invention has proposed, as shown in the Japanese Laid Open Pat. No. Sho-62-141345, an automatic transmission whose counter (drive) gear is situated coaxially with an input shaft near a center portion of the automatic transmission mechanism. With regard to the counter gear of the automatic transmission, one end of the counter gear is connected to a certain rotating element of a planetary gear unit, and another has a gear section, an outer surface of a boss section is supported by a supporting wall, through bearings, which is integrally constituted with the case.
The bearings are double tapered roller bearing, and its outer race has a brim section which bulges radially from a boss section, and a spline is formed at outer surface of the boss section, and a screw section is formed on another end of the outer race. A (second) one-way clutch is installed on an outer surface of the brim section. The spline formed on the boss section is coupled to the supporting wall, and a nut is set on the screw section, so that the nut and the brim hold the supporting wall.
Accordingly, to assemble the counter gear section, an engine side of a transaxle case is put downward, an outer race of a bearing is set on the case supporting wall. After turning over over the transaxle case, the outer race is fixed by fastening the nut. After this process, the counter, gear is installed with one of tapered bearing, further, after turning over the axle case again, another tapered bearing is installed. So the nut is set on the counter gear boss section so that certain pre-load is provided. Because of the above process, to assemble the counter gear section, the axle case are required to be turned many times. In addition, adjusting work such as fastening of the nut to fix the outer race, pre-load adjustment and caulking and the like have to be performed in the axle case, inevitably, such working process is laborious.
On the other hand, with regard to an automatic transmission for a front-engine-front-drive car, minimization of axial length is a critical issue when considering its mounting space. However, the above mentioned automatic transmission may cause problem on strength if the nut to hold the outer race toward the supporting wall is thin because the number of thread meshing with the nut is small. Consequently the nut needs certain thickness, which may increase an axial length.